Computer-based aids for earthmoving machines are becoming more common. For example, systems are being developed which utilize the Global Positioning System (GPS) satellites for determining the position of the machine and even the position of an earthmoving tool.
Other systems compile a data base of this position information. The database is continuously updated as the earthmoving machine modifies the site. One such system is disclosed in U.S. Pat. No. 5,493,494, issued to Henderson. The system disclosed by Henderson displays the vehicle on a video screen to aid the operator in operation of the machine. The database may include information related to the site, such as the position of points or sections of the work site in a site coordinate system.
As the earthmoving machine modifies the site, the site surface changes and the database must be updated. Positioning systems, such as GPS, may be used to determine the position of points located on the new or modified site surface.
Problems are encountered in such systems when attempting to determine the position in site coordinates of points on the site surface to an acceptable accuracy. For example, a GPS receiver determines the position of the GPS antenna, not the site surface. The accuracy of any position estimate for the site surface based solely on GPS will be inaccurate because the machine is moving, the machine is pitched and rolled with respect to the site surface, and there is a time lag between the time when a position estimate is accurate and the time the estimate is received.
The present invention is aimed at solving one or more of the problems as set forth above.